A variety of waste disposal devices exist which compact the waste in order to reduce the volume thereof. Among such known waste compaction systems are those which compact the waste by have a displaceable wall portion that is raised or lowered in order to reduce the size of the waste container and thereby compress the waste contained therein. For example, devices are known which employ a vertically displaceable bottom wall, a top cover fully closing an open top end of the container, and a driving system displacing the bottom wall upwardly to compress waste against the closed top cover. However, several disadvantages exist with such systems. For example, they do not allow waste to be received therein during the compression cycle, i.e. with the top cover in the closed position, and/or have a relatively complex configuration, and/or can inadvertently trap a hand or other body portion of a user with the top cover during the compression cycle, thus risking serious injury to the user. Accordingly, improvements are desirable.